ACTIONS ON ENZYMES II3 



of the narcotics on the dehydrogenases themselves. 

 The effect of the narcosis is on an earlier step as in- 

 dicated by the following diagram: 



O2 — Cytochrome oxidase 



I 



Cytochrome 



I I Region sensitive to low 



Flavoprotein ) -*- concentrations of narcotics 



Coenzyme 



Substrate — Dehydrogenase ■<- Region sensitive to high 



concentration of narcotics 



The views which Quastel has developed, outlined 

 above, refer only to the action of narcotics upon the 

 central nervous system of mammals, particularly of ro- 

 dents. 



Johnson and his colleagues have made some very 

 stimulating studies from a quite different point of view 

 on the effect of narcotics on bacteria. They found that 

 narcotic action can be antagonised by high pressure. It 

 had been noted that when protein denatures there is an 

 increase in volume. If this is prevented by compression, 

 no denaturation occurs. Johnson, therefore, argues that 

 since the action of narcotics can be reversed by high 

 pressure, the narcotics act by denaturing proteins and 

 not by adsorption on specific active centres of enzymes. 

 This view is, of course, quite compatible with the oil- 

 water partition coefficient hypothesis of Overton and 

 Meyer, for it is quite clear that lipoid substances can 



